Embodiments of the present technique relate generally to health monitoring, and more particularly to radar based methods and systems for monitoring a person in a resting state.
Sound sleep is generally beneficial and restorative for a person's health and exerts a great influence on the quality of life of the person. The human sleep/wake cycle typically conforms to a circadian rhythm regulated by a biological clock. The sleep cycle of a healthy person, for example, is characterized by a general decrease in metabolic rate, body temperature, blood pressure, breathing rate, heart rate, cardiac output, sympathetic nervous activity and other physiological functions. Accordingly, changes in such physiological parameters owing to disturbed or poor sleep quality are often indicative of deteriorating health of the person.
Monitoring sleep and wake patterns and various physiological parameters such as heart rate and respiration during sleep, thus, provides clinical markers for identifying and treating various health conditions afflicting a subject. These health conditions, for example, include insomnia, obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea collapses the upper airway, thus restricting the flow of air to the lungs even in the presence of an ongoing respiratory effort, while also causing detrimental changes in the subject's heart rate. Central sleep apnea, however, results in a complete loss of respiratory effort leading to a loss of air to the lungs and eventually lowering the oxygen in the blood.
Other common sleep disorders in adults include conditions such as Periodic Limb Movements Disorder (PLMD) and Restless Legs Syndrome (RLS). In PLMD, the subject makes characteristic repetitive movements every 30-40 seconds leading to sleep disruption. In RLS, the subject has an overwhelming desire to move or flex their legs as they fall asleep, again leading to disrupted sleep patterns. Accordingly, monitoring such anomalous body movements during the resting state is useful in identifying and treating various heath conditions of the subject.
To that end, a clinically accepted sleep diagnostic technique employs a sleep laboratory, where the subject is connected to a polysomnography (PSG) machine that records multiple physiological parameters. A sleep laboratory evaluation, however, requires the subject to be tethered to multiple cables with electrodes attached to their torso and head, often resulting in disruptive sleep patterns due to anxiety and/or physical discomfort. Particularly in the case of children (pediatrics), it is exceedingly difficult to assure connections well enough to assess sleep health. Additionally, the use of such complex and intrusive equipment necessitates monitoring the subject at a dedicated testing facility with trained technicians, often costing over a thousand dollars per night.
Certain other sleep monitoring systems employ air bladders, vibration and other electronic and motion sensors disposed in a mattress or bed of the subject to monitor the subject's movements and sleep patterns. These systems, however, require use of customized beds and mattresses that may not suit the subject's comfort or liking. Furthermore, these systems are often unable to prevent gross motion of the subject from affecting the heartbeat and respiration readings leading to inaccurate measurements. Accordingly, certain companies have employed rather complex radar systems for non-contact pulse and respiration measurements for short term monitoring. Many of these sensors and systems, however, incur inhibitive cost and complexity for monitoring the subject continuously.
It is desirable to develop unobtrusive and cost-effective methods and systems for monitoring a person in a resting state. Specifically, there is a need for efficient sleep monitoring systems and methods that non-intrusively yet reliably measure various motion and physiological parameters to determine sleep metrics corresponding to the subject. Furthermore, it is desirable to develop systems that do not require contact or line-of-sight to the subject's body and are capable of accurately assessing the health of the subject.